1. Field of the Invention
The present invention relates to a battery array having a plurality of rectangular battery cells stacked with intervening separators, and in particular to a battery array optimally suited as a power source installed on-board an electric-powered vehicle such as a hybrid vehicle (hybrid car) or electric vehicle (electric automobile) to supply power to a motor that drives the vehicle.
2. Description of the Related Art
A battery array for automotive applications has many battery cells connected in series to increase output voltage and power. Considering charging capacity per unit volume, a battery array has been developed that arranges many rectangular battery cells in a stack.
For example, refer to Japanese Laid-Open Patent Publication 2010-86887.
In the battery array cited in JP 2010-86887, angled binding bars are attached to retain the rectangular battery cells in a stack. The ends of the binding bars are attached to endplates disposed at each end of the rectangular battery cell stack.
With this battery array, it is difficult to reliably prevent up-and-down vibration of the rectangular battery cells held between the binding bars. In particular, when used in a vibration inducing environment such as in a vehicle, rectangular battery cell vibration cannot be reliably prevented. Specifically, when a battery array with many rectangular battery cells stacked between intervening separators is installed in a vibration inducing environment, rectangular battery cells disposed in the center region vibrate up-and-down. In this situation, vibration of the centrally located rectangular battery leads to various detrimental effects. For example, insulating layers established on the surfaces of vibrating rectangular battery cells can rub against non-vibrating binding bars to cause leakage currents or insulation breakdown. In addition, vibration can physically damage individual rectangular battery cells and result in detrimental effects such as degraded electrical characteristic or reduced lifetime.
Rectangular battery cell vibration can be reduced by tightening the binding bars to apply more pressure on the battery stack. However, with this structure, not only is it difficult to reliably prevent vibration by tightening the binding bars, but other detrimental effects are generated by applying excessive pressure on the rectangular battery cells. For example, damaging effects such as separator distortion, which can prohibit stable battery cell cooling, or rectangular battery cell distortion, can result.
The present invention was developed with the object of avoiding the detrimental effects described above. Thus, it is a primary object of the present invention to provide a battery array that prevents rectangular battery cell vibration with an extremely simple structure and can effectively avert various detrimental effects caused by vibration.